镉离子在H2SO4溶液中极谱行为的研究

本文研究了在没有动物胶的0.5M H_2SO_4溶液中镉离子的极谱行为,得到了如下的结果:(1)在0.050～20.0mM CdSO_4 0.5M H_2SO_4的十种溶液中测得的电流-电位曲线都有良好的波形、恒定的极限扩散电流和易于确定的半波电位.这些曲线上都没有极谱极大出现;其极限扩散电流(波高)与镉离子的浓度成正比.在镉离子低浓度(0.050～0.20mM)时,半波电位保持不变,在镉离子高浓度(1.00～20.0mM)时,也仅有很小的变化.故镉离子在0.5MH_2SO_4,溶液中的电流-电位曲线可供定量和定性测定之用.(2)镉离子在低浓度时的极谱波是一种可逆波.(3)前人在H_2SO_4溶液中研究镉离子时之所以没有能得到令人满意的极谱行为的原因是他们在H_2SO4溶液中添加了动物胶的缘故.(4)作者从得到的波形良好的电流-电位曲线上,测定了25±0.2℃时镉离子在0.5M H_2SO_4溶液中的扩散电流常数、半波电位和电极反应中得失的电子数.结果如下: i_d/cm~(2/3)t~(1/6)=3.97μA/mM·mg~(2/3)·s~(-1/2) E_(1/2)=-1.011V(0.5M硫酸亚汞电极)=-0.559V(饱和甘汞电极) n=2 这些数据比Lingane的数据,扩散电流常数2.6μA/mM·mg~(2/3)·s~(-1/2)和半波电位-0.59V(饱和甘汞电极)],要合理些.

The polarographic behavior of cadmium ion in H2SO4 solution

It was found that the polarographic behavior of cadmium ion in 0.5M H2SO4 solution containing 0.01% gelatin is unsatisfactory because the diffusion current does not attain a perfect constant value but continues to increase gradually up to the potential of hydrogen discharge. The polarographic behavior of cadmium ion in 0.5M H2SO4 solution without gelatin is studied in this work. It is found that the polarographic behavior of cadmium ion in 0.5M H2SO4 is excellent. The current-potential curves of cadmium ion in 0.5M H2SO4 solutions in which the concentration of cadmium varies from 0.050mM to 20.0mM are determined and the well-defined polarographic waves with limiting diffusion current and easily determined half-wave potential are obtained. The limiting diffusion current (wave height) of cadmium ion in 0.5M H2SO4 is proportional to its concentration. The half-wave potential of cadmium ion only varies slightly in the range of -1.011--1.047V (vs. 0.5M mercurous sulfate electrode) as the concentration of cadmium ion varies from 0.05mM to 20.0mM. Therefore, cadmium can be determined quantitatively and qualitatively by polarographic method in H2SO4 solution. The following polarographic data of cadmium ion in 0.5M H2SO4 solution are obtained: the diffusion current constant id/cm2/3t1/6= 3.97\m\A/mM.mg2/3.S-1/2 the half-wave potential E1/2=-1.011V (vs. 0.5M mercurous sulfate electrode) or K1/2=-0.559V (vs. SCE), and the number of electron transferred in the electrode reaction n=2.